EP2945160B1 - Josephson junction electronic component - Google Patents

Description

The present invention relates to electronic components having a Josephson junction. More particularly, it relates to fast logic circuits, called RSFQ (Rapid Single Flux Quantum), based on such components, in order to achieve operating frequencies of the order of a few hundreds of GHz.

In known manner, a Josephson junction comprises first and second layers made of a superconducting material, separated from each other by an intermediate layer made of a non-superconducting material.

In a superconducting medium, the charge carriers are constituted by the association of two electrons, within a pair of Cooper. In the so-called "conventional" superconductors, the associated electrons have opposite spins, the Cooper pair then having a zero spin. The statistic followed by a Cooper pair gas is a Bose-Einstein statistic, according to which several Cooper pairs can simultaneously occupy the same quantum state. In particular, at a temperature below a critical temperature, all Cooper pairs condense in the same fundamental quantum state.

As a result, the charge carrier gas is macroscopically described by a quantum wave function. This has a phase θ .

In a Josephson junction, although the continuity of the superconducting material is interrupted by the presence of the non-superconducting material of the intermediate layer, there is a coupling between the charge carrier wave functions in the first and second superconducting layers.

Indeed, according to the Josephson effect, the wave function of the charge carriers of the first superconducting layer extends through the intermediate layer, into the second superconducting layer where it interferes with the wave function of the carriers of the superconducting layer. charge of the second superconducting layer.

The current-voltage characteristic of a Josephson junction, whose intermediate material is a metal, is schematically represented in FIG. figure 1 .

$$V=\frac{{\mathit{\Phi }}_0}{2\mathit{\pi }}\frac{d\varphi }{dt}$$

Où

• Le paramètre ϕ = θ ₁ - θ ₂ correspond à la différence entre les phases des fonctions d'ondes des porteurs de charge dans les première et seconde couches supraconductrices, respectivement ;
• Φ ₀ est une constante caractéristique de l'effet Josephson et s'exprime en fonction de la constante de Planck h et de la charge de l'électron e selon : ${\mathrm{\Phi }}_{\mathrm{0}}=\frac{\mathrm{h}}{\mathrm{2}\mathrm{e}};$
  
• R est dénommée résistance normale et correspondant à la pente des branches asymptotiques de la caractéristique courant - tension ;
• t représente le temps ; et,
• I_c est un courant critique, caractéristique de la jonction Josephson.

It is shown that the current I and the voltage V take the following parametric form: $$I=\frac{{\mathit{\Phi }}_0}{2\mathit{\pi R}}\frac{d\phi }{dt}+I_{\mathrm{vs}}\mathit{sin\phi }$$

$$V=\frac{{\mathit{\Phi }}_0}{2\mathit{\pi }}\frac{d\phi }{dt}$$

Or

• The parameter φ = θ ₁ - θ ₂ corresponds to the difference between the phases of the wave functions of the charge carriers in the first and second superconducting layers, respectively;
• Φ ₀ is a characteristic constant of the Josephson effect and is expressed as a function of the Planck h constant and the charge of the electron e according to: ${\mathrm{\Phi }}_{\mathrm{0}}=\frac{\mathrm{h}}{\mathrm{2}\mathrm{e}};$
  
• R is called normal resistance and corresponds to the slope of the asymptotic branches of the current - voltage characteristic;
• t represents the time; and,
• I _c is a critical current, characteristic of the Josephson junction.

There is a solution for which the phase difference φ is constant over time. Voltage V is zero, but DC can be circulated through the Josephson junction. This direct current is less than I _c , because of the term in sinφ in relation (1).

There is also a solution for which the voltage V is constant and not zero. The phase difference is then an increasing monotonic function as a function of time. An oscillating current in sinφ crosses the Josephson junction.

It will be noted, without going into detail, that the characteristic parameter I _c is a function of the component of the magnetic field in a plane transverse to the stacking direction of the layers of the Josephson junction.

For use in a fast logic circuit RSFQ, or for example still as an oscillator or mixer in any circuit, it is necessary to be able to control the operating mode of the Josephson junction to switch it to active mode (in operation: "ON"), in which the current flowing in the junction oscillates; either in idle mode (out of operation: "OFF"), in which the current flowing in the junction is continuous.

Until now, a means available to control a Josephson junction is to change the bias (voltage V or current I ) applied to it to go from inactive mode to active mode, and vice versa.

In a fast logic circuit, to generate the control voltage of a main Josephson junction, it is common to use a Josephson junction matrix, which in turn requires to be permanently in active mode. Thus, the energy balance of such a fast logic circuit is very unfavorable. As in any electronic system, there is also the problem of the dissipation of the energy supplied to the system.

This constraint in the manner of controlling a Josephson junction limits the possible uses of the corresponding electronic components.

On the other hand, another way to control a Josephson junction is described in the document US 2011/267878 A1 . This discloses a random access memory having a matrix of cells, each cell being a hysteresis magnetic Josephson junction device. More specifically, a device consists of a component SQUID (Superconducting QUANTUM Interference Device) whose two Josephson junctions respectively incorporate a ferromagnetic element consisting of a first ferromagnetic elementary magnetization fixed layer and a second layer. ferromagnetic elementary variable magnetization, separated from each other by an additional layer, such as an oxide layer. The variable magnetization of the second layer is modified by a suitable write current.

The invention aims to overcome this problem.

For this, the subject of the invention is a circuit according to the claims.

• la figure 1 est un graphe courant-tension générique d'un composant électronique du type à jonction Josephson ;
• la figure 2 est une représentation schématique d'un premier mode de réalisation d'un composant électronique à jonction Josephson destiné à être intégré dans un circuit selon l'invention ;
• la figure 3 est une représentation schématique d'un second mode de réalisation d'un composant électronique à jonction Josephson destiné à être intégré dans un circuit selon l'invention ; et,
• la figure 4 est une représentation schématique d'un troisième mode de réalisation d'un composant électronique à jonction Josephson destiné à être intégré dans un circuit selon l'invention ; et,
• la figure 5 est une représentation schématique d'un quatrième mode de réalisation d'un composant électronique à jonction Josephson destiné à être intégré dans un circuit selon l'invention

The invention and its advantages will be better understood on reading the description which will follow, given solely by way of illustrative and nonlimiting example, and with reference to the appended drawings in which:

• the figure 1 is a generic current-voltage graph of an electronic component of the Josephson junction type;
• the figure 2 is a schematic representation of a first embodiment of a Josephson junction electronic component intended to be integrated in a circuit according to the invention;
• the figure 3 is a schematic representation of a second embodiment of a Josephson junction electronic component intended to be integrated in a circuit according to the invention; and,
• the figure 4 is a schematic representation of a third embodiment of a Josephson junction electronic component intended to be integrated in a circuit according to the invention; and,
• the figure 5 is a schematic representation of a fourth embodiment of a Josephson junction electronic component intended to be integrated in a circuit according to the invention

Referring to the figure 2 a first embodiment of a Josephson junction component will be presented.

According to this first embodiment, the component 10 results from the stacking, in a stacking direction X, of a first layer 1, a first polarizer 2, an intermediate layer 3, a second polarizer 4, and a second layer 5.

The first and second layers, 1 and 5, are made of a superconducting material. It is preferably a high critical temperature superconductor material, ie exhibiting superconducting properties for temperatures in the range of 25 to 120 ° above absolute zero (-273 ° C). ). This is for example a mixed oxide of copper and yttrium barium, called YBCO. The oxide YBa ₂ Cu ₃ O ₇ is preferably used.

A thickness of the first and second layers, 1 and 5, may be arbitrarily selected a priori. However, the minimum thickness depends on the material used. For YBCO, the thickness of the first and second layers is chosen between 5 and 50 nm, preferably between 20 and 40 nm, more preferably equal to 30 nm.

The intermediate layer 3 is made of a conductive material of the electric current. The material of the intermediate layer is chosen for example from complex oxides, such as LaNiO ₃ oxide, normal elementary metals, such as Cu copper, Ag silver, Au gold, etc., or semiconductors.

A thickness of the intermediate layer 3 must be less than a length L _N called the coherence length in the conductive material, which depends on the material actually used for the intermediate layer. For example, for LaNiO ₃ , the thickness is chosen between 0.1 and 100 nm, preferably the shortest possible, for example equal to 20 nm.

The first and second polarizers, 2 and 4, are made of a ferromagnetic conductive material. This ferromagnetic material is preferably a manganite oxide of lanthanum strontium, called LCMO according to the corresponding acronym. A ferromagnetic medium having the formula La _0.7 Ca _0.3 MnO ₃ is preferably used.

The first polarizer 2 has a first magnetization M2 in a first direction of magnetization. In a simple embodiment, the first magnetization M2 is constant in direction and intensity during use of the component and is perpendicular to the stacking direction.

The second polarizer 4 has a second magnetization M4. The second magnetization M4 is constant in intensity, but its direction and direction relative to the first direction of magnetization varies during the use of the component. In the simple embodiment, only the direction of magnetization M4 varies according to the first direction of magnetization, which is constant.

A thickness of the first and second polarizers, 2 and 4, is chosen to be less than a coherence length L _P in the ferromagnetic material. In the case of LCMO, the thickness is preferably between 0.1 and 100 nm, preferably equal to 5 nm.

The physical principle used in the present component is the Andreev effect. This effect is known and presented for example in the article TM Klapwijk, "proximity effect from an Andreev perspective," Journal of Superconductivity: Incorporating Novel Magnetism, Vol. 17, No. 5, October 2004 .

This effect takes place at the interface between a conducting medium and a superconducting medium.

According to this effect, an electron moving in the conductive and incident medium on the interface with the superconducting medium can lead to the transmission of a Cooper pair in the superconductor and the reflection of a hole in the conductive medium.

The conservation of the pulse imposes that, if the electron has a p (vector) pulse, the Cooper pair will have a pulse 2.p and the hole, a pulse -p.

If the electron has a spin s , the hole has either a spin -s (the electron-hole pair then constituting a singlet whose total spin is zero), or a spin s (the electron-hole pair constituting a triplet whose total spin equals unity).

In the first case, a so-called conventional supercurrent is generated through the interface. The conventional supercurrent carries a charge but no spin.

In the second case, an unconventional supercurrent is generated through the interface. This requires a so-called "spin-flip" process at the interface between the superconducting medium and the conductive medium, which is present especially when the conductive medium is a ferromagnetic medium (for example of the LCMO ). The unconventional supercurrent carries a charge and a spin.

As a result of this effect, the wave function of the electron / hole pairs in the conducting medium is coupled, at the interface, with the wave function of the Cooper pairs of the superconducting medium.

Since the unconventional supercurrent is spin polarized, it is sensitive to polarization effects at the interface between the conductive medium and the superconducting medium. The presence of a polarizer (having a determined magnetization) at the interface between the conducting medium and the superconducting medium makes it possible to select, among the electrons or the incident holes, the electrons or the holes whose spin is parallel to the magnetization of the polarizer and, therefore, those who can actually participate in the flow of an unconventional supercurrent through the interface.

In the component presented above, a polarizer 2, respectively 4, is provided at the interface between the intermediate layer 3 and the superconducting layer 1, respectively 5, so as to control the unconventional supercurrent at each interface.

In addition, the electron / hole pairs generated at an interface may flow in the intermediate layer 3. For example, an electron / hole pair generated at the interface between the intermediate layer 3 and the second superconducting layer 5 carrying an unconventional supercurrent, can flow through the intermediate layer 3 to the interface between the intermediate layer 3 and the first superconducting layer 5 to participate in an unconventional supercurrent at this interface.

As a result, there are bound states between the electron-hole pairs in the intermediate layer and the Cooper pairs in the first superconducting layer 1 and in the second superconducting layer 5. Thus, there is interaction between the wave functions of the charge carriers of the first and second superconducting layers, via a mechanism for generating and transmitting electron / hole pairs through the intermediate layer.

In order to effectively introduce a coupling between the wave functions of the first and second superconducting layers together, the thicknesses of the ferromagnetic layers 2 and 4 and of the intermediate layer 3 are chosen as a function of the coherence length L _P of the electron / hole pairs in the ferromagnetic material and the coherence length L _N of the electron / hole pairs in the intermediate material. For example, the smallest coherence length between these two lengths is chosen as a constraint.

dans le régime balistique, ou $$l_i=\sqrt{\frac{\hslash D_{\mathit{i}}}{2\mathit{\pi KT}}}$$

dans le régime diffusif. Où

• T est la température absolue ;
• K est la constante de Boltzmann ;
• ℏ est la constante de Planck réduite ;
• v_Fi est la vitesse de Fermi dans le matériau i ; et,
• D_i est la constante de diffusion électronique dans le matériau i.

In general, for a material, the coherence length is written: $$l_i=\frac{\hslash {\mathrm{<figure-callout\; id="2"\; label="v\; Fi"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">v\; </figure-callout>}}_{\mathit{Fi}}}{2\mathit{\pi KT}}$$

in the ballistic regime, or $$l_i=\sqrt{\frac{\hslash D_{\mathit{i}}}{2\mathit{\pi KT}}}$$

in the diffusive regime. Or

• T is the absolute temperature;
• K is Boltzmann's constant;
• ℏ is the reduced Planck constant;
• v _Fi is the Fermi velocity in material i ; and,
• D _i is the electron diffusion constant in the material i .

The measurements of the coherence length L _P show that it is greater than 30 nm in the LCMO.

Taking into account the Fermi v _FN speed which is approximately 10 ⁵ m / s in the LaNiO ₃ , the coherence length L _N is longer in this material than the length L _P (and this especially as the conductive material is brought to low temperature), and even longer in metals such as Au or Ag.

By placing a polarizer at each interface between the intermediate layer and the superconducting layers, a polarizer / analyzer assembly is created to control the relative polarization of the unconventional supercurrent through each interface: If the first and second magnetizations are antiparallel (180 °) between them), none of the charge carriers, electron or hole generated at the first interface with a spin parallel to the first magnetization, can, after circulation through the intermediate layer, pass through the second polarizer and reach the second interface. No superconducting current will be able to cross the Josephson junction. This one will be in a blocked state.

On the other hand, when the first and second magnetizations are parallel to each other (0 °), a charge carrier, electron or hole, generated, at the first interface, with a spin parallel to the first magnetization, may, after circulation through the intermediate layer, cross the second polarizer and reach the second interface where it can participate in the generation of a current. A superconducting current can therefore flow through the Josephson junction. This one will be in a passing state.

The component 10 thus comprises a control means 12 adapted to modify the orientation of the second magnetization M4 along the magnetization direction to place the component in the on state, in which the first and second magnetizations are parallel to each other. or in a blocking state, wherein the first and second magnetizations are antiparallel to each other.

The control means 12 consists, for example, of a circuit making it possible to apply a current pulse along a wire positioned appropriately in the vicinity of the second polarizer 4. A pulse of current I _ON in a first direction makes it possible to place the second magnetization parallel to the magnetization direction; a current pulse I _OFF in a second direction, opposite to the first, makes it possible to place the second magnetization antiparallel to the direction of magnetization.

The component 10 may comprise a first source 14 of electrical bias to apply a first bias current or a first bias voltage between a terminal 8 in contact with the first layer 1 and a terminal 9 in contact with the intermediate layer 3. In the presently envisaged embodiment, the first source 14 is a source of a first bias current I _bias1 .

The component 10 may comprise a second current source 16 adapted to apply a second bias current bias _bias2 between a terminal 6 in contact with the first layer 1 and a terminal 7 in contact with the second layer 5.

The component 10 may comprise a device 18 for measuring the voltage capable of detecting a voltage between first and second layers 1 and 5.

A second embodiment will be described with reference to the figure 3 . Elements of the second embodiment similar or identical to those of the first embodiment are indicated by the same reference numeral.

The component 10 comprises a substrate 20. The material of the substrate is for example sapphire, SrTiO ₃ , etc.

An intermediate layer 3 covers the substrate 20.

A free upper face of the intermediate layer 3, opposite to a lower face in contact with the substrate 20, carries first and second electrodes 26 and 27, respectively.

The first electrode 26 results from the superposition of a first polarizer 2 made of a ferromagnetic material and a first layer 1 made of a superconducting material.

The second electrode 27 results from the superposition of a second polarizer 4 in a ferromagnetic material and a second layer 5 of a superconducting material.

The first and second layers 1 and 5, the first and second polarizers 2 and 4 and the intermediate layer 3 are similar to the corresponding layers of the first embodiment of the figure 2 , in terms of material and thickness.

The first and second polarizers 2 and 4 are advantageously produced simultaneously during a step of growth of a ferromagnetic material. They then have the same thickness.

The first and second layers 1 and 5 are advantageously produced simultaneously during a step of growth of a superconducting material. They then have the same thickness.

Given the dimensions mentioned above, a technology for producing such a component is electron beam lithography.

The control means 12 comprises a wire disposed near the second polarizer 4 so that a current I _ON or I _OFF flowing in the wire produces a magnetic field capable of modifying the orientation of the magnetization M4 of the polarizer 4.

A first electric polarization source 14 capable of generating a first bias current can be connected between the intermediate layer 3 and the first superconducting layer 1.

A second electrical bias source 16 capable of applying a second bias current may be connected to terminals 6 and 7 provided on each of the electrodes 26 and 27.

On the figure 4 still another embodiment of the component 10 is shown. This embodiment is similar to that of the figure 2 , except that the layers 1 and 2 have a reduced cross-sectional extension with respect to the layer 3. In this way, the layer 2 does not cover the whole of a contact surface of the layer 3, which can then receive the injection terminal 9 of the first _bias current I when it exists.

It should be noted that the direction of the first and second bias currents indicated in the figures is arbitrary and can be adjusted as appropriate, depending on the application of the component.

Alternatively, it is the magnetization M2 of the layer 2 which is controlled during the use of the component 10 and not the magnetization M4.

To the figure 5 another embodiment of the component is shown. In this embodiment, the component 110 has no intermediate layer of a normal material and comprises a single layer 130 of ferromagnetic material.

The first and second polarizers 102 and 104 then consist of zones of the ferromagnetic layer 130, in line with the first and second superconducting layers 1 and 5, respectively.

The intermediate separation between the first and second polarizers 102 and 104 is then constituted by a wall 103 between magnetization domains. The wall 103 constitutes the boundary between a domain of the ferromagnetic layer 130 having a magnetization in a first direction and a domain of the ferromagnetic layer 130 having a magnetization in a second direction different from the first.

The wall 103 is movable towards the first electrode 126, so as to extend the domain corresponding to the second polarizer 104, or to the second electrode 127, so as to extend the domain corresponding to the first polarizer 102, thanks to a control means 112 constituted by a ferroelectric layer, a grid and an electrode.

The ferroelectric layer 140 is disposed between the substrate 120 and the ferromagnetic layer 130. It is for example composed of a bismuth ferrite oxide, or BFO (for "Bismuth Ferric Oxide" in English).

The substrate 120 is here composed of Niobium-doped STO (Nb: STO), so that the substrate 120 is made of a current-conducting material so as to constitute a gate.

The ferroelectric layer 140 has a localized residual dielectric bias P. The polarization P is a vector, as shown schematically on the figure 5 . The orientation of the polarization P is regulated by a voltage pulse between the metal electrode 142 placed under the substrate 120 and the electrodes 6 and / or 7 (so as to regulate the orientation of the polarization P in line with the electrodes 126 and / or 127 respectively).

The orientation of the polarization P in a zone of the ferroelectric layer 140 modifies the anchoring of the magnetization of the zone adjacent to the ferromagnetic layer 130.

Thus, by regulating the polarization distribution P in the ferromagnetic layer 140 in the presence of an external magnetic field, the magnetization domains of the ferromagnetic layer 130 can be extended or reduced, i.e. the wall 103 can to be moved.

Depending on the position of the wall 103, the two polarizers 102 and 104 may belong to the same domain and have the same magnetization, the component 110 is then passing, or belong to different domains and have different magnetizations, preferably antiparallel, the component being then blocking.

So here we have a mechanism for controlling Josephson's junction.

It should be noted that in this embodiment, by dispensing with an intermediate interface in a normal material, the distance between the first and second layers 1 and 5 is chosen as a function of the coherence length L _P in the material ferromagnetic polarizers 102 and 104 only.

• Dans un premier mode de fonctionnement, adapté à un composant 10 ne comportant qu'une première source 14 de polarisation électrique, l'une des interfaces supraconducteur/ferromagnétique joue un rôle passif, c'est-à-dire que le courant ne circule pas à travers la couche ferromagnétique correspondante. Sur le montage de la figure 3, des électrons sont injectés dans la couche intermédiaire 3 au moyen d'un courant de biais I_bias1. Pour cela, une source 14 est connectée entre la couche intermédiaire 3 et, par exemple, la première couche 1 supraconductrice, aux moyens de bornes adaptées 9 et 8. Par conséquent, c'est l'interface entre les couches 4 et 5 qui est ici passive. L'avantage de ce premier mode de fonctionnement réside en ce que le courant circule uniquement dans une moitié du composant, limitant ainsi la dissipation d'énergie.

Component 10 (or 110) has three modes of operation:

• In a first mode of operation, adapted to a component 10 having only a first source 14 of electrical bias, one of the superconductive / ferromagnetic interfaces plays a passive role, that is to say that the current does not circulate through the corresponding ferromagnetic layer. On the assembly of the figure 3 electrons are injected into the intermediate layer 3 by means of bias current I _bias1 . For this, a source 14 is connected between the intermediate layer 3 and, for example, the first superconducting layer 1, to the means of adapted terminals 9 and 8. Therefore, it is the interface between the layers 4 and 5 which is here passive. The advantage of this first mode of operation is that the Current flows only in one half of the component, thus limiting energy dissipation.

In this first mode of operation, if the current I _bias1 is beyond the critical current I _c , when the component is switched into the on state ( I _ON ), a superconducting oscillating current flows through the interface between layers 2 and 3. On the other hand, when the component is in the off state ( I _OFF ), no alternating current flows through the component 10.

In a second mode of operation, adapted to a component 10 comprising only a second bias current source 16, a bias current source 16 is provided, _{capable of} applying a current I _bias2 , between terminals 6 and 7 of the component 10, so as to allow, when in the on state, the circulation of an oscillating superconducting current (active state of the Josephson junction).

In this second mode of operation, if the current I _bias2 is such that one is in the part of the current-voltage characteristic of the Josephson junction beyond the critical current I _c (cf. figure 1 ), when the component is switched in the on state ( I _{ON )} , an oscillating current flows through the component. On the other hand, when the component is in the off state ( I _OFF ), no alternating current flows through the component, although the applied voltage is non-zero and a direct current flows through the component.

In a third mode of operation, currents I _bias1 and I _bias2 are applied simultaneously.

In this third mode of operation, if the sum of the currents I _bias1 and I _bias2 is such that one is in the part of the current-voltage characteristic of the Josephson junction beyond the critical current I _c , when the the component is switched into the on state ( I _{ON )} , an oscillating current flows through the component. On the other hand, when the component is in the off state ( I _OFF ), no alternating current flows through the component, although the applied voltage is non-zero. Low electrical power is required to control the component. The advantage of this third mode of operation is to separate the implementations of the functions of supply and threshold (condition described below).

Thus, an electronic component Josephson junction can be controlled other than by a variation of the voltage applied between its terminals is obtained. The control of the change of state of the component is a magnetic field pulse, which can be caused by the circulation of a control current pulse (in or near the ferromagnetic layer).

Since the component is sensitive to variations in the magnetic field, a magnetic pulse modifying the magnetization of one of the polarizers so as to switch the component from the blocking state to the on state or vice versa, a use of this component as a sensor variations of the magnetic field is possible.

Although the principle of the present component can be implemented by means of low temperature superconducting material, the use of high temperature superconducting materials is preferable in particular to allow the integration of the electronic component in RSFQ circuits implemented in portable micro-cryogenic systems.

Claims (15)

1. A supraconductor circuit of a « Rapid Single Flux Quantum » - RSFQ type, comprising a local oscillator, characterised in that said local oscillator is a Josephson junction component (10, 110) of the type comprising first and second layers (1, 5) made from a superconducting material, separated one from the other by :

   - an intermediate interface (3, 103), made from an electrically conductive material; and,

   - first and second polarizers (2, 4), made from a ferromagnetic material, the first polarizer, having a first magnetisation (M2), being interposed between the intermediate interface (3, 103) and the first layer (1), and the second polarizer, having a second magnetisation (M4), being interposed between the intermediate interface (3, 103) and the second layer (5),

   the component further comprising a control means (12, 112) able to modify at least one magnetisation among the first and second magnetisations to place the component either in an on state, wherein the first and second magnetisations are parallel one with the other, or in an off state, wherein the first and second magnetisations are antiparallel one with the other.
2. Supraconductor circuit according to claim 1, wherein a distance between the first and second layers (1, 5) is chosen, according to a coherence length (L_N) of the charge carriers in the intermediate interface (3) and/or a coherence length (L_P) of the charge carriers in the polarizers (2, 4 ; 102, 104), between 0,1 nm and 200 nm, preferably between 5 nm and 100 nm, more preferably equal to 40 nm.
3. Supraconductor circuit according to claim 1 or claim 2, wherein the superconducting material of the first and second layers (1, 5) is a superconducting material with a high critical temperature.
4. Supraconductor circuit according to claim 3, wherein the superconducting material with a high critical temperature is YBCO.
5. Supraconductor circuit according to any one of the claims 1 to 4, wherein a thickness of the first and second layers (1, 5) is chosen between 20 and 40 nm, preferably 25 and 35 nm, more preferably equal to 30 nm.
6. Supraconductor circuit according to any one of the claims 1 to 6, wherein the ferromagnetic material of the first and second polarizers (2, 4 ; 102, 104) is LCMO.
7. Supraconductor circuit according to any one of claims 1 to 6, wherein a thickness of the first and second polarizers (2, 4) is chosen between 3 and 10 nm, preferably equal to 5 nm.
8. Supraconductor circuit according to any one of claims 1 to 7, wherein, the intermediate interface being made of an intermediate layer (3), the material of said intermediate layer (3) is a normal metal, chosen among normal metal oxides or elementary normal metals.
9. Supraconductor circuit according to any one of claims 1 to 8, wherein a thickness of the intermediate layer (3) is chosen between 15 and 25 nm, preferably equal to 20 nm.
10. Supraconductor circuit according to any one of the claims 8 to 9, wherein the first layer (1), the first polarizer (2), the intermediate layer (3), the second polarizer (4) and the second layer (5) are successively stacked along a stacking direction.
11. Supraconductor circuit according to any one of the claims 8 to 9, comprising a substrate (20) in contact with one surface of the intermediate layer (3) opposite the surface of the intermediate layer (3) in contact with the first and second polarizers (2, 4), the material of the substrate being preferably chosen among sapphire and SrTiO₃.
12. Supraconductor circuit according to any one of the claims 1 to 7, wherein the intermediate interface s made by a Bloch wall (103) between magnetisation domains in the ferromagnetic layer (130), that extends between the first and second supraconducting layers (1, 5).
13. Supraconductor circuit according to any one of the claims 1 to 12, comprising first and second electrodes (26, 27 ; 126, 127), the first electrode resulting from the stacking of the first polarizer (2, 102) and the first layer (1) and the second electrode resulting from the stacking of the second polarizer (4, 104) and the second layer (5).
14. Supraconductor circuit according to any one of the preceding claims, characterised in that it comprises a source (14, 16) of electric bias (I_bias1, I_bias2).
15. Supraconductor circuit according to any one of the preceding claims, characterised in that it comprises a voltage measuring device (18) able to measure the voltage across the first and second layers (1, 5) of the component.

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